What is CVE-2026-85873?

CVE-2026-85873 is a medium-severity vulnerability in Microsoft Skype For Business Server 2015 Cu13, classified under Authorization Bypass Through User-Controlled Key. CVSS score: 6.5/10. Published 2026-10-13.

How severe is CVE-2026-85873?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Auth bypass in Microsoft Skype For Business Server 2015 Cu13

CVE-2026-85873

Improper authorization in Skype for Business and Microsoft Lync allows an authorized attacker to elevate privileges over a network.

Vulnerability class: IDOR (Insecure Direct Object Reference)

Published 2026-10-13 · last modified 2026-10-13.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Weakness classification (CWE)

CWE-639 — Authorization Bypass Through User-Controlled Key

References

Skype for Business Elevation of Privilege Vulnerability (vendor-advisory, patch)

Frequently asked questions

What is CVE-2026-85873?: CVE-2026-85873 is a medium-severity vulnerability in Microsoft Skype For Business Server 2015 Cu13, classified under Authorization Bypass Through User-Controlled Key. CVSS score: 6.5/10. Published 2026-10-13.
How severe is CVE-2026-85873?: Medium severity. CVSS v3 base score is 6.5 out of 10.